Web transport control assembly



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A T TQRNEYS United States Patent 3,388,875 WEB TRANSPORT CONTROL ASSEMBLY Edwin Zucker, Rochester, N.Y., assignor to Xerox Corporation, Rochester, N.Y., a corporation of New York Filed Oct. 1, 1965, Ser. No. 491,991 11 Claims. (Cl. 24275.51)

ABSTRACT OF THE DISCLOSURE Apparatus for transporting web material over a printing zone in a contact printer in which the web material passes from one storage roll to another and is driven at high speeds by a capstan assembly in contact with the web material intermediate the two storage rolls. A pair of storage loop assemblies one associated with each storage roll forms a pair of loops in the web material which vary in response to the web material being advanced by the capstan assembly. As the storage loop assemblies are displaced, a responsive signal is generated to drive a torque motor which in turn rotates the respective storage roll to either increase or decrease the slack accordingly. A pair of rotational damper assemblies one associated with each storage roll provides a variable rotational damping force to the respective storage roll in response to the quantity of web material wound thereon.

BACKGROUND OF THE INVENTION This invention relates to photography and, more particularly, to apparatus for transporting web materials in a contact printer.

In contact printing, as the name implies and as understood in the art, a sensitized duplicating film paper or the like is exposed on physical contact with the negative to be reproduced. As used herein, the term negative is intended to encompass a transparency in which the image can be either a negative or positive in a photographic to be made on a contact printer, it is necessary to employ a continuous feed system for both the duplicating material and the negative to be reproduced. It is common to thread photographic web materials, as, for example, film, from a supply spool to various directional idlers that help guide the film across the printing zone and onto a takeup spool. Normally, film advance and rewind are effected through a drive connected to the takeup spool and supply spool, respectively. Inherently, this technique for transporting film places undue stresses on the film which must undergo high rates of acceleration especially when reversing direction. It has been found that even slight stresses to delicate film, such as that used in aerial photography, tend to stretch or otherwise distort the image thereon and, therefore, detract from the degree of dimensional integrity required in this type of photograph y SUMMARY OF THE INVENTION In accordance with the present invention, the film transport system is provided with an automatic tensioning assembly which maintains a predetermined storage loop at both the supply and receiving ends to allow for high rates of acceleration.

It is, therefore, an object of this invention to provide apparatus for transporting web materials at high rates of acceleration.

It is another object of this invention to provide apparatus capable of rapidly positioning photographic web materials in a contact printer.

It is still another object of this invention to provide proper tensioning for web materials transported at high rates of acceleration.

3,388,875 Patented June 18, 1968 "ice It is a still further object of this invention to provide a transport apparatus for web materials capable of rapid reversals without subjecting the materials to undue stresses.

These and other features and objects of the invention will be apparent from the following description and from the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a perspective view of the exterior of the contact printer apparatus hereof;

FIGURE 2 is an enlarged view of the control panel;

FIGURE 3 is an isometric view of the contact printer apparatus;

FIGURE 4 is a side elevation of the contact printer with the doors removed;

FIGURE 5 is an end view of the contact printer apparatus;

FIGURE 6 is a plan view of the window shade assembly;

FIGURE 7 is an enlarged view of the storage loop assembly with portions broken away to show internal structure;

FIGURE 8 is a front view of FIGURE 7;

FIGURE 9 is a view of the variable coefficient damper assembly with portions broken away to show internal structure;

FIGURE 10 is a view of the transport capstan assembly;

FIGURE 11 is a block diagram of the system for starting and stopping the film transport;

FIGURE 12 is a longitudinal sectional view of the film drive support;

FIGURES 13A through 13F are sectional views of the film drive support taken along lines A-A through F-F, respectively, of FIGURE 12;

FIGURES 14 and 15 are a plan and side view, respectively, of the articulated idler assembly;

FIGURES l6 and 17 are side elevation and plan views, respectively, of the film gate assembly partly broken away to show internal components;

FIGURE 18 is an end view of the gate assembly taken along line 18-18 of FIGURE 16;

FIGURE 19 is a sectional view of the lamp house assembly taken along line 19-19 of FIGURE 16;

FIGURE 20 is another sectional view of the lamp house assembly taken along line 2020 of FIGURE 17;

FIGURE 21 is a block diagram illustrating the exposure control system;

FIGURE 22 is a schematic electrical diagram of the separation amplifier for the exposure control system; and

FIGURE 23 is an electrical circuit diagram of the scan drive and gate assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGURE 1 of the drawings, the apparatus includes a cabinet 11 having a control panel 12 on which are mounted various selector knobs, buttons, and indicators used for controlling the operation of the machine. For example, certain controls are used to set the printing cycle, while others determine inputs to the automatic exposure control system in a manner which will become apparent. Observation by an operator of the frame position of the negative is obtained through a glass viewed 14 adjacent the control panel. The interior of the printer is protected from light entering through viewer 14 by a suitable light shield not shown. On the sides of the cabinet are sliding doors 15 through which entry may be made for loading the negative and duplicating material and for general servicing of the apparatus. 

